1. Field of the Invention
This invention relates to a front wheel stabilizing device for an electric motor-driven wheeled vehicle, more particularly to a front wheel stabilizing device to prevent tipping of the wheeled vehicle.
2. Description of the Related Art
A conventional electric motor-driven wheelchair is generally provided with a front wheel stabilizing device to improve tracking upon undulating or irregular surfaces and to provide anti-tip stability. FIGS. 1 and 2 show an electric power wheelchair 10 disclosed in Taiwanese patent publication No. 370866. The wheelchair 10 includes a main frame 11, two front drive wheels 12 mounted proximate to a front side of the main frame 11, two rear caster wheels 13 mounted on a rear aide of the main frame 11, and a footrest 14 and two front stabilizing devices 15 mounted on the front side of the main frame 11.
Each of the front stabilizing devices 15 includes a support rod 151 which extends through an insert hole 112 formed in a front upright post 111 of the main frame 11 and which is secured to the front upright post 111 by means of screw fasteners 16 that extend through lock holes 113 formed in the front upright post 111, a cantilever arm 152 which is pivotally mounted on the front upright post 111, a stabilizing wheel 153 which is mounted on the cantilever arm 152, and a compression spring 154 which is disposed between a front segment 1511 of the support rod 151 and the cantilever arm 152.
Due to the provision of the front stabilizing devices 15, when the wheelchair 10 travels over undulating or irregular surfaces, the compression springs 487 provide a damper effect to the cantilever arms 152 and the stabilizing wheels 153 so as to improve anti-tip stability. However, the upright posts 111 need to be formed with the insert holes 112 for passage of the support rods 151, and the lock holes 113 for securing the support rods 151 to the upright posts 111, thereby resulting in weakening of the structure of the main frame 11 and complicating the manufacturing process. Moreover, as the front segments 1511 of the support rods 151 extend forwardly of the main frame 11 for the compression springs 154 to be mounted thereon, they are liable to be damaged as well as unsightly.
U.S. Pat. Nos. 5,848,658 and 6,460,641 also disclose electric power wheelchairs, which, however, suffer from the aforesaid drawbacks as well.